Studies are continuing on the interaction between adenovirus and host cell control mechanisms by studying several situations in which the outcome of infection includes malignant cell transformation and/or abortive virus replication. One of those systems under study is the abortive infection of hamster cells with adenovirus type 12, which leads to induction of cellular DNA synthesis, followed by neoplastic transformation of a small fraction of the cell population. The primary goal is to develop an understanding of the nature of the viral genes which interact with the cell controls, initiating a cycle of cellular DNA synthesis. A second system under study is one in which the nature of those cell factors necessary for virus replication is being investigated by attempting to determine which human chromosomes must be present in a human-mouse cell hybrid for it to be capable of supporting virus replication. Third, the virus inhibitory factor (VIF) present in adenovirus-induced tumor cells is being further purified and characterized. Lastly, the mechanisms by which arginine deprivation severely restricts adenovirus replication is continuing to be investigated, as are the effects of arginine deprivation on the uninfected host cell.